In a semiconductor manufacturing process, transferring patterns on a reticle to a substrate is an important step. Transferring patterns on a reticle to a substrate includes spin-coating a photoresist layer on the substrate; performing a photolithography process on the photoresist layer to form the corresponding patterns in the photoresist layer; and etching the substrate using the patterned photoresist layer as an etching mask. The exposure light used for the photolithography process is often an ultraviolet (UV) light. The photolithography process is realized by exposing the photoresist layer using an exposure apparatus and a reticle having transparent slits. The transparent slits are corresponding to the patterns. That is, the patterns are formed by the transparent slits. Thus, after the photolithography process, the patterns formed by the transparent slits are transferred to the photoresist layer to form the patterned photoresist layer. After etching the substrate using the patterned photoresist layer as an etching mask, the patterns formed by the slits with certain widths and shapes are formed on the substrate.
The reticle can also be a half-tone reticle. FIG. 1 illustrates an existing half-tone reticle. As shown in FIG. 1, the half-tone reticle includes a substrate (not labeled). The substrate includes an UV light blocking region 101 which entirely blocks the UV light irradiating from the exposure apparatus, and an UV light transparent region 102 which entirely transmits the UV light irradiating from the exposure apparatus. Further, the substrate also includes a plurality of semi-UV transparent regions, such as a first semi-UV light transparent region 103 and a second semi-UV light transparent region 104, etc., which partially transmit the UV light irradiating from the exposure apparatus.
The UV light transmitting through the UV light transparent region and the semi-UV light transparent regions has different exposure intensities. Thus, the patterns formed in the photoresist layer have different thicknesses. Accordingly, after etching the substrate using the patterned photoresist layer as an etching mask, the patterns formed on the substrate have different heights or depths. That is, using the half-tone reticle is able to form patterns with different heights in the substrate by a single exposure process.
Because such an approach is based on the transmittances of the material of the semi-UV light transparent region, if a plurality of semi-UV light transparent regions with different transmittances are needed to be formed on a substrate, it needs a plurality of different materials with different transmittances; and it may also need different fabrication steps. Thus, the fabrication process of a half-tone reticle having more than two different semi-UV light transparent regions with different transmittances are relatively complex. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems.